DE1479548B2 - PROCESS FOR MANUFACTURING ROTATIONAL SYMMETRIC PLASTIC MOLDED PARTS IN THE SPINNING PROCESS - Google Patents

Description

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The invention relates to a method for producing rotationally symmetrical molded plastic parts in the centrifugal process, with the plastic and filler in any proportions as well as reinforcement material introduced into the centrifugal mold in any number of consecutive operations and be thrown.

It is already known to use rotationally symmetrical molded plastic parts, in particular pipes, in a centrifugal process to manufacture. In the case of the centrifugal process, it was previously in a with or possibly also without separating agent -staggered, z. B. made of copper, aluminum, steel or other metals Hollow form the appropriate amount of synthetic resin and filler in one or more consecutive Operations introduced into the centrifugal mold and spun. Possibly put for the production of reinforced, rotationally symmetrical molded plastic parts, glass fiber mats in hollow molds and soaked it with cast resin. By the action of centrifugal force Mixing and distribution takes place, with the presence of a reinforcement this being clings to the centrifugal mold and the hardening that begins in and of itself during the centrifugation usually with additional heating, e.g. B. in air-heated ovens, must be accelerated. Through the However, the application of heat during the centrifugal process is, on the one hand, very expensive and heatable Ovens are necessary, which ensure the setting of a constant temperature as far as possible. at Choosing other centrifugal shapes, pipe thicknesses and / or casting resins is the setting of a new temperature required, so that there is hardly any case that various synthetic resins or synthetic resins can be spun in different shapes at the same temperature without the Disadvantages of insufficient curing to be accepted. If the heating is neglected during the centrifugal process are very incompletely cured and therefore sticky, rotationally symmetrical Plastic molded parts received. This somewhat incomplete hardening is also often found in the molded parts, the hardening of which has been accelerated by the application of heat. One could Therefore, do not use centrifugally produced parts immediately or store them together, as the parts tend to stick together.

The object of the present invention is to control the curing and, if necessary to accelerate.

The solution to this task is, according to the invention, that accelerators, activators, Catalyst and pigment with any distribution of the amount by weight to be introduced and any Distribution to the substances to be introduced in the work steps.

If necessary, a faster hardening is achieved by changing the centrifugal force values than with the molded parts produced by previously known centrifugal processes.

Due to the great diversity of the substances that can be divided into the individual work steps and their weight ratios, variations in the curing time and the property of the rotationally symmetrical shaped body are made possible. However, the curing time is in any case shorter than that for the molded parts produced using the same resins and the same or similar additives according to the previously known centrifugal processes with comparable, but often improved quality, this quality improvement on the one hand by controlling the course of the polymerization and on the other hand by a better mixing is achieved by adding the accelerators and catalysts separately in the centrifugal process. ₅ . .

It is particularly useful that in a first step only part of the prepolymer or of the monomer is centrifuged and the remaining part or another. Prepolymer or a another monomer mixture is centrifuged in one or more subsequent operations will. ■ ·,

All hardenable synthetic resins, especially polyester resins, coumarone, indene, Epoxy resins, polyacrylates and polymethacrylates, but also polyvinyl compounds, e.g. B. polyvinyl chloride, suitable. Surprisingly, it was found that when using monomers or Prepolymers a greater mechanical strength is achieved than when using the polymers or the solvent-containing polymers themselves.

The known inorganic or organic fillers are suitable as fillers in this process

or other mixtures, such as. B. sand, rock flour, Slate flour, chalk, kaolin, talc, asbestos, glass powder, metal powder, hardened plastic beads, Barite, clay gel and mica powder. The fillers can either be used in one operation or be centrifuged in distributed over several work steps and expediently at the same time with an activator or promoter, the additives optionally using a varnish can be fixed. After the fillers or part of them have been centrifuged in, accelerators can be added and / or the catalyst optionally with the remaining part of the binder and / or Color pigments are centrifuged, with only the joint centrifugation of accelerator and activator and promoter should be avoided in one operation. Particularly useful is to contain a certain percentage of the filler and activator in the first working stage To spin the monomer mixture or the prepolymer and then use the spin mold Catalyst solution, color pigment, accelerator and residues of the filler optionally in several To feed operations. Furthermore, good results are achieved if one is in a first stage of work the synthetic resin mixture mixed with accelerators or the prepolymer in advance and in one in the second work stage, a filler mixture mixed with a catalyst solution and activator is centrifuged, the filler mixed with the activator can also be separated as desired, only then the Catalyst solution can be centrifuged. When using accelerators together, In particular, those based on peroxide with fillers, care must be taken that no filler is present, which causes an immediate decomposition of the peroxide, otherwise the centrifugation would have to be carried out ■ the components are carried out separately in several work stages.

If you want to achieve an even better mixture or distribution of the injected substances, so According to the invention, the constituents introduced in the centrifugal mold can be passed through into the centrifugal mold protruding steel combs, rods, small rolls, wires, etc. are mixed. This creates turbulent mixing flows, which cause a more intensive mixing. By the change the centrifugal forces can also, but to a lesser extent, have an improved mixing effect caused, because an increase in centrifugal forces mainly causes a Improvement of the inner surface.

The fillers used can have any grain size. However, it turned out to be useful Use grain sizes below 2 mm. If you want pipes reinforced with filler with high mechanical strength To obtain strength, the most homogeneous grain sizes possible should be used or fillers should be added that contain more than 50% grain sizes with a diameter in a ratio of 1: 0.4 stand.

The starting materials for the production of the rotationally symmetrical shaped bodies are monomers or prepolymers of known curable synthetic resins with added catalysts, activators, promoters and, if appropriate, plasticizers, fillers and pigments. Promoters are understood to mean compounds which additionally enhance the effectiveness of the "catalyst accelerator" system, e.g. B. Dimethylaniline, Socyanate, nitrous acid and sodium nitrite. For example, rotationally symmetrical shaped bodies containing unsaturated polyester, preferably peroxidic accelerators such as benzene peroxide, lauryl peroxide and tertiary butyl hydroperoxide, were added. The activators known per se, such as cobalt naphthenate and cobalt octoate, served as activators, and dimethylaniline (promoter) was used as a further additive. The processing of the epoxy resins or acid anhydrides in the presence of BF ₃ complexes or other accelerators was preferably carried out with amines or amides as curing agents and optionally with the addition of crosslinking agents. Another advantageous possibility of variation arises when using epoxy resin / polyester mixtures or prepolymers or monomer mixtures. "-Polyvinyl chloride additives in the centrifugal process are expediently used as prepolymers in a mixture with polyvinyl acetate or polyacrylic acid esters or using copolymers or in a mixture with their monomers or prepolymers. Even when casting resins other than polyester resins are used, monomers or their Pre-polymerizates and the division of the substances to be introduced in the centrifugal process in several work steps are very advantageous, since better mixing and hardening of the centrifugal parts, combined with improved high mechanical properties (impact resistance, etc.), is achieved. B. fillers, pigments, etc., take place.

For the inner coating of the pipes, you can, if necessary, even before the end of the spinning process other resins suitable for the interior coating or their prepolymers, e.g. B. polyvinyl chloride compounds, possibly using fillers, additives such as catalysts, Pigments, accelerators, activators or plasticizers, centrifuged and optionally before further re-centrifugation, reinforcements are added to the partially hardened, centrifuged molding compound, z. B. glass fibers, fabric, etc., can be thrown in, if necessary, this After centrifugation swelling agents or monomers are used.

Claims (4)

Patent claims: 1. Method for producing rotationally symmetrical Plastic molded parts in the centrifugal process, in which plastic and filler in any proportions as well as reinforcement material in introduced into the centrifugal mold and spun in any number of successive operations are, characterized in that accelerators, activators, promoters, Catalyst. and pigment among any Distribution of the weight to be introduced and any distribution of the substances to be introduced in the operations will. 2. The method according to claim 1, characterized in that in a first operation only part of the prepolymer or the monomer is spun and the remainder or another prepolymer or another monomer mixture in one or more subsequent ones Operations is centrifuged. 3. The method according to claim 1, characterized in that in the centrifugal mold first tissue immersed in an accelerator or activator solution and then introduced the monomer or prepolymer mixture containing the catalyst is added. 4. Process according to Claims 1 to 3, characterized in that the introduced into the centrifugal mold Components through steel combs, rods or rollers protruding into the centrifugal mold be mixed.